1. Field of the Invention
The present invention relates to an image processing device and method and an image display device and method, and more particularly to a frame interpolation process that interpolates new image frames between existing image frames.
2. Description of the Related Art
Liquid crystal displays and other displays of the hold type display the same image continuously for one frame period. A consequent problem is that the edges of moving objects in the image appear blurred, because although the human eye moves continuously while following a moving object, the moving object moves discontinuously, one frame at a time. One possible countermeasure is to smooth out the motion of the object by interpolating frames, thereby increasing the number of displayed frames.
A related problem, referred to as judder, occurs in content created by converting filmed footage such as a movie to a television signal. Because of the different frame rates of the two (the filmed footage and the television signal), two or three frames in the resulting image signal may have been created from the same original frame. If the image signal is displayed as is, motion appears blurred or jerky.
Judder also occurs when computer-processed video is converted to a television signal without further change, because two frames of the resulting television picture are generated from the same computer-processed frame.
In conventional image processing devices and methods, one finds the zero-order hold method, which interpolates an image identical to the preceding frame, and the mean value method, in which the interpolated frame is the average of the preceding and following frames. The zero-order hold method, however, fails to produce smooth motion in an image that moves in a fixed direction, leaving the problem of blur in hold-type displays unsolved. With the mean value interpolation method, there is the problem that moving objects acquire ghosts.
A remedy proposed in U.S. Pat. No. 7,586,540 and corresponding Japanese Patent Application Publication No. 2006-129181 (p. 8, FIG. 3, now Japanese Patent No. 4359223) generates each interpolated pixel in the interpolated frame from the most highly correlated pair of pixels in the preceding and following frames that are in point-symmetric positions with the interpolated pixel as the center of symmetry. Since this method detects correlation between individual pixels, however, a large correlation between pixels in areas of quite different image content is sometimes detected, in which case a correctly interpolated frame cannot be generated.
Conventional frame interpolation processing as described above is plagued by the problems of blurred or jerky motion (judder) and the interpolation of incorrect frames due to false correlation detection. The disruption of interpolated frames becomes particularly evident when an image element appears and disappears in the preceding and following frames.